1. Field of the Invention
This invention relates to an electromagnetic stepping motor operable in either direction of rotation.
2. Description of the Prior Art
French Pat. No. 2,209,251, for example, illustrates such a motor comprising two coils which are activated one after the other to produce rotation of the rotor of the motor in one directional sense or the other, by steps each of 180.degree.. Each coil must be dimensioned so as to furnish, by itself, the energy necessary for this rotation, that is to say each coil must have the same volume as the coil of a conventional stepping motor which can rotate in only one directional sense.
Swiss patent application Ser. No. 10,768/71 illustrates a stepping motor operable in either direction of rotation and comprising only one coil, but the rotor in this case rotates by 360.degree. at each step. This is is a drawback from the point of view of the mechanical arrangement since the step-down ratio between the motor and the members it drives is of importance.
U.S. Pat. No. 4,112,671 illustrates a stepping motor operable in either direction of rotation which comprises only one coil and the rotor of which rotates by only 180.degree. at each step. An electronic circuit controls the rotation in one directional sense or the other. This type of motor has the serious drawback however that, if a step is by chance missed or if the motor makes one step too many, the direction of rotation is reversed.